The present invention generally relates to a surface mount contact configured to be carried in an electrical component, such as a socket. More particularly, the present invention relates to a surface mount contact which has multiple contact beams.
Contacts are used in a variety of applications to connect conductive members, such as processors, circuit boards and the like. In many applications, the contacts are held in a housing such as a socket. For example, a socket is generally used to connect a processor to a circuit board. The typical socket includes a body having cavities that carry several flexible contacts. A land grid array (LGA) socket holds the contacts that have a flexible body formed at one end with a contact beam and attached at an opposite end to a solder ball. The contact beam extends upward from the cavity above the top surface of the body of the socket, while the solder ball extends downward from the cavity below the bottom surface of the body. The cavities are arranged in an array and the contacts are oriented with all of the contact beams extend from the cavities in the same direction such that the contact beams in each row are aligned with one another. The solder balls attached to the contacts are soldered to electrical traces on the circuit board. The processor has several contact pads on its bottom surface and the processor is positioned on the socket such that each contact pad is aligned with a corresponding single contact beam. The processor is compressed downward onto the socket with each contact beam engaging a corresponding contact pad.
As technology advances, contacts are needed that can carry data signals at faster rates and that are more responsive to state transitions in the data signal. Sockets are also needed that are more reliable and can be manufactured at lower costs. The ability to improve these factors is affected by the socket size, as well as the internal electrical performance of the socket, such as the inductance and resistance exhibited by the contacts. A reduction in socket size allows smaller printed wiring boards to be used and creates shorter circuit paths which aid state transition response time.
Conventional sockets suffer from several drawbacks. The contacts are large and take up a large amount of space within the socket. The socket thus carries a limited number of contacts and has a limited capacity to transmit signals between the processor and the circuit board. Additionally, the contact beams are limited in size and length in order that the contact beams do not touch contact beams in the same or different rows when deflected by the processor. Short and/or small contact beams have a more limited range of vertical deflection that longer and/or larger contact beams. If the shorter, smaller contact beams are overly deflected, they become permanently deformed. Larger, longer contact beams may require too much force to be properly joined to the processor.
Further, each contact beam creates a local electromagnetic (EM) field when it carries data signals. As the contact beams are positioned closer and closer, the EM fields begin to interfere with the performance of adjacent contact beams. This interference appears as an increase in the inductance of the contacts. As inductance increases, the contacts in the socket respond more slowly to transitions in the voltage level of signals carried through the socket. Hence, while a data signal output from the processor to a contact may switch voltages (or states) in a few micro seconds, once the data signal passes through the corresponding contact in the socket, the data signal changes states over a longer period of time. It is desirable to limit the inductance exhibited by contacts to maintain the ability to quickly respond to state changes.
Moreover, as contacts are made smaller, electrical signals encounter more resistance when traveling through the contacts and thus the socket. High resistance causes the contacts to generate heat as electrical signals pass therethrough which can damage surrounding parts and shorten product life. Additionally, more energy is required to convey electrical signals through high resistance contacts which causes the electronic device to consume more energy.
A need exists for a socket and contact that addresses the above noted problems and others experienced heretofore.